The Centre for Alternative Technology - The Wales Institute for Sustainable Education

The Wales Institute for Sustainable Education (WISE) is a 2,000m² education centre located at the Centre for Alternative Technology (CAT), which is situated in an old slate quarry in the foothills of Snowdonia. The construction site is brown field, being located on the slate tip.

CAT was founded in 1974 to demonstrate sustainable ways of living and to inspire, inform and enable practical solutions for sustainable living. It consists of a 16ha site, 4ha of which are open to the public as a visitor centre. WISE is located at the rear of the site, tucked up against the slope of the old slate tip and adjacent to the original slate cutting sheds, now used as a restaurant.

The design process started with ‘Planning for Real’ sessions, involving the building’s users. These determined the building’s location, along with space and sustainability requirements. Schematics were developed from the alignment of existing buildings towards the north and the slate tip to the east. These elements meet at an angle of 10 degrees. Various options were sketched and gradually the final design emerged with the theatre located at the pivot of these two alignments.

The building is constructed around a series of courtyards, maximising light and giving a strong sense of space and connection with the outside world. CAT lies in a high rainfall area and this is dramatically expressed in the rainwater system of the building. Run-off cascades from terrace to terrace until it is concentrated by spouts into shallow pools in the central courtyard from where it drains via the old quarry’s waterwheel pit. Daylight, sunlight and reflected light are brought into the spaces from many different directions, so that there is always an awareness of time and weather, and every space can open to the sounds and smells of nature.

The use of materials and construction methods with low embodied energy has been essential to building design at CAT. An additional aim with WISE was to develop sustainable building techniques further so that a conventional contractor could manage them. This process was aided by the use of a PPC2000 Partnering Contract, which allowed for early appointment of the main contractor and their involvement in the design process. The main elements of WISE are:

• A structural glulam timber frame.
• Solid timber decks supporting the first floor terrace. These are constructed of 150x50mm timbers screwed together into cassettes that sit into rebates in the main frame.
• Galvanized steel bracing that support all of the timber frames.
• The glulam frame is encased in 500mm of a hemp-lime mix finished with a self-coloured sand-lime render. This gives twice the insulation value required by building regs and also ensures good air-tightness where it encases the frame joints.
• Thermal mass is provided by unfired clay bricks and a spectacular 15m diameter, 7m high rammed earth lecture theatre.
• Stainless steel drum shaped roof. Suitable for use in warm or cold ventilated situations. The passive ventilation will also benefit by minimizing heat loss in winter.
• Wherever possible the foundations used lime concrete. Where the building is constructed on the inclined slate tip it was necessary to use reinforced concrete. However, 50% of the cement was replaced with GGBS to minimize environmental impact.
• Internal floors are of local ash, softwood and rubber.
• All finishes are natural with minimal or zero VOC content.
• The building fabric is almost 100% reusable or recyclable at the end of its life.

Sustainability also extends to the M&E systems:

• The electrical fit-out specified no PVC wherever possible.
• Air handling units use low velocity fans and heat reclaim.
• The building is connected to CAT’s district heating system. A wood-fired CHP unit is being commissioned to provide heat for the building and the rest of the site.
• 70m² of evacuated tube solar water heating has been installed on the building to provide hot water for showers in the summer months.

Additional investments were made in order to minimize environmental impact and to ensure that building performance can be tested against targets. These additional measures include:

• Changes to the scheme to improve air tightness
• The solar water heating system
• The 6.5kW PV array
• Significant additional investment in the building management system to allow detailed monitoring of energy performance
• Funding of a PhD student who is investigating the performance of the hemp-lime walls
• Sourcing of funds for a second PhD looking into the carbon footprint of the building

Performance targets were set as follows:

An essential element of the project, and a key aspect of its sustainable credentials, is monitoring of performance against these targets. Full data will not be available until the building has been in full operation for a year, but early indications are that targets are being achieved.